The present invention relates to a document reading apparatus for use in a facsimile system capable of keeping the surface of a reading base plate, mounted on the top surface of a document conveying device, always clean so that the quality of an image signal read out from a document is highly improved.
Heretofore, as shown in FIG. 1, a light beam from a light source 1 irradiates to a reading base surface 2' of reading base plate 2 and then a reflected light therefrom is reflected again by reflectors 3, 3' to a light-electricity converting element 5. Said reflected light is read out by the light-electricity converting element 5 through a lens 4 and recorded to a memory device (not shown). Then, the image data of the document conveyed according to the operation of a driving roller 6 is read out by the light-electricity converting element 5 in the same operation as abovementioned, and converted to an electric signal to be transmitted to an external device.
However, since the conventional document reading device, as aforementioned, of which reading base plate 2 is formed with a plane surface, is located at a position so as to contact the document 7 thereto conveyed by the driving roller 6, there is a disadvantage in that the reading base surface 2' becomes contaminated by dust stuck on the document.
Accordingly, when the reading base plate is contaminated, the reflecting rate of the light irradiated from the light source is lowered. However, when any difference occurs in to the light reflecting rate between the reading base plate and the document, an undesirable blotted image is produced on the received recording paper, so that a document with a clear image can not be obtained.